Treatment of gases or vapors with liquids



Oct. 28, 1952 6, DIXON 2,615,832

TREATMENT OF GASES OR VAPORS'WITH LIQUIDS Filed 001;. 8, 1946 2 SHEETS-SHEET l Patented st. 28, 1952 TREATMENT OF GASES OR. VAPORS WITH LIQUIDS Olaf George Dixon, Norton-on-Tees, England, as-

signor to Imperial Chemical Industries Limited, a corporation of Great Britain Application October s, 1946, Serial No. 702,048 In Great Britain June 16, 1943 liquids it .has been customary to'provide large surfaces on which intimate contact'between' the fiuid and liquid can take place. For example, there have been used columns packed with filling bodies manufactured from a wide variety of materials and having a wide variety of shapes, such filling bodies being irregularly placed 1. e. random packed in the column or have been arranged according to a regular pattern. In an endeavour to obtain enhanced efiiciency it has been proposed "to use as the packing of such columns, hollow filling bodies in the form, for example, of cylinders, saddles and truncated cones, such filling bodies being made from wire netting or gauze. While the' use of columns packed with filling bodies made from wire netting or wire gauze was attended by improved efficiency as compared with columns packed withfilling bodies having solid 'walls, such as porcelain or metal rings, it was recognised that they were not entirely satisfactory. In the case of distillation columns packed with filling bodies made from wire netting or wire gauze improved results could be obtained by giving the filling bodies in the column a preliminary wetting by running the column at a rateabove its capacity until it'became completely flooded followed by reducing the rate of distillation until the flood subsided and then setting the rate at the point'desired for distillation.

The present invention provides a process whereby there is obtained improved operation of columns packed with filling bodies, when used, for example, in distillation, adsorption and extraction processes.

According to the present invention there is provided a process for treating :fluids with liquids in a column at least a part of which is packed as hereinbefore defined, with substantially hollow filling bodies made from woven material,

the apertures of the woven material being of such a size that they can be maintained completely sealed by the liquid under the operating conditions, in which prior to treating the said fluids with liquids the column is flooded with liquid so as toseal the said apertures, introducing liquid at the top of thecolumn at a rate such that on defiooding' the column the said openings under the operating conditions are:

Claims. (Cl. 202-40) maintained completely sealed with the liquid being used, subsequently 'deflooding the column, while maintaining the rate of flow of the fluid being treated sufiiciently low so as not to break the said sealing;

When substantially hollow filling bodies are used, they may, if desired, be freely packed as hereinafter defined. .In this specification a column is understood to be freely packed with filling bodies when at any cross sectionthe ratio of the smallest cross-sectional dimension of the packed column to the greatest dimension of the filling bodies at that section is not less than 4 to 'l, irrespective of Whether the column is random packed i. e. packed indiscriminately with filling bodies or whether they are arranged according to a regular pattern. r

.An essential feature of the invention, when filling bodies made from woven materials are used, is that the apertures in the filling bodies are maintained completely sealed With theliquid being used.- This condition may be established by completely flooding the column with liquid and thereafter maintaining a sufiicient fiow cf liquid down the column to maintain the sealing. The minimum rate of liquid flow down the column for maintaining complete sealing-of the .apertures in the filling bodies will depend for' example, on the surface tension of the liquid being used, the material from which the filling :bodies are made, the size of the apertures in the filling bodies andthe rate of flow-of thefiuid being treated,but can be readily determined by a simple preliminary trial of the apparatus.

It is recognized that the broad idea of flooding distillation columns prior to use is conventional, as shown, e. g, in Industrial-.andEngineering Chemistry, Industrial EditionBO (.1938) ,page 297,

and Analytical Edition 1939, page 285. In contradistinction to this known method, the present invention employs one of the following procedures for wetting the filling bodies, in each .of which, it will be noted, the rate of fiow ofgas or vapour up the column during both the flooding and the defiooding is .never substantially above that at which the process (e. g.,with complete'sealing of the openings of the filling bodies continuously maintained) is to be operated.

' Theqcolumn should be flooded with theliquid to beused-by one of thefollowing methods.

Method A.Liquid is introducedat the top of the column and a temporary hold up of the liquid arranged at the bottomlof the column, for .exampla'bymea-ns of an adjustable orifice until the column is ccmpletely full of liquid. .A fter flooding the column, a rate of flow of liquid down the column is arranged such that when filling bodies made from woven materials are used the quantity of liquid is at least sufiicient to maintain the apertures in the packing sealed with liquid under the conditions of operation. With the forms of packing made from other than woven material hereinafter defined, the rate of flow of liquid down the column should be sufficient to maintain the operation of the column at its highest efficiency at the desired gas M vapour velocity up the column.

In the case of distillation apparatus this fiow of liquid may be obtained as reflux liquid When this flow of liquid is arranged the column is gradually deflooded by opening the adjustable orifice.

Method B.In the case of a packed column attached to a boiler for distillation purposes and fitted with a reflux condenser, the boiler, and if necessary part of the column may be completely filled with liquid to be distilled and subsequently heated, whereby the liquid boils and ascends the column and completely floods the packing therein. Then, after adjusting the rate at which reflux liquid is returning to the column to that at which either the apertures of the packing of the column can be maintained completely sealed, or at which the column is operating at its highest efficiency at the desired gas or vapour velocity up the column when the forms of packing other than woven material hereinafter defined are used, liquid is removed from the boiler until a suitable level is attained and distillation is commenced, ensuring that reflux liquid continues to flow down the column at the above-mentioned rate.

Method C.In distillation apparatus, the column may be isolated from the boiler and filled with the cold liquid to be distilled whereby the packing is completely flooded. The liquid is then allowed to fiow into the boiler and heating commenced, at the same time continuously circulating a portion of the liquid to the top of the column, whereby the column is maintained full of liquid, until the quantity of reflux liquid passing down the column will be sufiicient to maintain the sealing of the apertures in any packing materials made from woven material, or with the forms of packing made from other than woven material hereinafter defined, sufiicient to maintain operation of the column at its highest efficiency, whereupon the circulation of liquid can be stopped. By this means the column is gradually defiooded but the reflux liquid continues to flow down the column at the above mentioned rate.

As a modification of the process I have also found that improved results are obtained in contacting gases or vapours with liquids in columns which are packed with filling bodies made from woven material, the said filling bodies being other than in the form of hollow filling bodies, if the hereinbefore defined methods of flooding are applied to the said columns.

The process of the present invention may be applied to the treatment of gases or vapours with liquids in columns packed with, for example, so called Berl saddles made from woven material or fiat fragments of woven material which may be twisted into a propeller-like shape or bent into a curved cross-section. Further examples of suitable filling bodies are those made from strips of Woven material which are formed into a helix or a form analogous to a spiral staircase, that is in the form of step-wise ascending spirals, and which have diameterssubstantially equal to that of the column in which they are to be used. Examples of filling bodies according to this feature of the invention are described in. Industrial and Engineering Chemistry Analytical Edition, at the following places, Lecky and Ewell 12 (1940) pages 545-547; Bower and Cooke 15 (1943) pages' 290-293.

The process of the present invention is also applicable to those types of column packed with hollow filling bodies made from woven materials, which bodies are not freely packed as herein-- before defined, for example improved results are obtained by applying the process to columns packed with the filling bodies described in British specification No. 536,552.

Furthermore, improved results are obtainedby the application of the process of the present invention to columns random packed or systematically packed with lengths of filamentous material such as glass wool, slag wool or wire, which may be bent or twisted into regular or irregular geometrical forms, for example into helices, or when the filamentous material is in short lengths it may be sent into single turn helices or into uniplanar forms such as rings or polygons. When filamentous material is packed irregularly in a. column the individual filaments intertwine with adjacent filaments and/or with parts of themselves to give a mass of packing having a large number of interstices. This is particularly the case where short lengths of filamentous material which are bent or twisted are used. An example of short lengths of filamentous material bent into single-turn helices for use as a packing material is described by Fenske in Industrial and Engineering Chemistry 26 (1934) page 1169, while examples of long filaments formed into a regular geometrical shape are described by Podbielniak in Industrial and Engineering Chemistry Analytical Edition 13 (1941) pages 639 to 645. While defiooding columns packed with such filamentous material, and subsequent thereto, liquid should be introduced continuously at the top of the column at a rate suflicient to maintain the operation of the column at its highest efficiency at the desired gas or vapour velocity up the column.

This liquid rate is easily determined by simple preliminary tests.

We have also found that the process of the present invention is particularly advantageous when applied to columns packed with fragments of material having a foraminate structure such as pumice and expanded shale, which preferably is in fragments of such a size that they are freely packed as hereinbefore defined. When using foraminate material as a column packing, it is necessary, while defiooding the column and subsequent thereto, to introduce liquid continuously at the top of the column at a rate sufficient to maintain the operation of the column at its highest efficiency, at the gas or vapour velocity up the column which it is desired to use. This rate of liquid is easily determined by simple preliminary tests. It should be understood that it is desirable to avoid the use of foraminate material which is liable to be attacked by any of the gases, vapours or liquids to be used in the column.

Figures 1, 2, 3 and '4 illustrate the shapes of hollow filling bodies made from woven material and Figure 5 one form of apparatus suitable for use in the process of the present invention. As hereinbefore stated these filling bodies are made '5 from woven material, but for clarity the individualthreads of the 'wQvenmateriaI are :not :shown in the drawings. Figure "fi illustrates theli results obtainable from a distillation 'columnoperated according to the :process or the present inven- :tion. 1

"Figure 1 shows an =open-ended cylinder, :Fi'gure 2 shows anopemended cylinder iwith allon- Jgitudinal gap in its -walll, -1 igure 3 ishows-an op'enend'ed cylinder with a longitudinal gap in its wall and an inner partition, an'd Figure it shows .:a strip fdf woven material wound into an open spiral.

The filling bodies made from woven material may be prcdu'ced rroma wide'variety of materials, for example, wire gauze, or Ltrom :lothi spaced apart by not=more-than-0.022 inch. A

wire gauze having substantially the same number of wiresinthe warp and weft is particularly "suitable :for .use according to the present invention, sand ittis preferred that in such gauze the distance between adjacent parallel wires is 'between 00050 inch and 0.0075 inch.

lI'he .rllling bodies .madeifrom woven material .;may-b'e produced: in a wide variety .of shapes but when .hollow f'filling .bodies "are :to the used, 5101' @2559 715i manufacture .itzis preferred to use those having the shapes illustrated in Figures .-1 :to 24,

although .it :should "be understood that the process of the present invention is not limited to the use of hollow fillingbodieshaving these shapes.

When hollow .cylindrical filling :bodieswith or without longitudinal gaps and/or longitudinal partitions or open spiral-form filling bodies are -used, they.-may;suitably have their lengths equal to their maximum width. For the best =e'fii- .ciencies their :length and maximum width :should preferably not 'bexgreat'er than 9/ iinc'h.

While the process of the present invention is applicable to various processes in which intimate contact' betweenz fluids and liquids is desired, for example, in .gas washing and absorption :processes, :it is particularly-suitable:for use in distillationiprocesses. Thuslin'distillationprocesses using columns random packed with open=ended :solid "walled cylinders 1 inchby ,1/ inch, the numberoitheoretical'plates :per foot of column length, as calculated by the method referred to bycLecky and Ewell in. lndustrial.-'and Engineering Chemistry, Analytical Edition, 1940, page #544, is 'usually about .3 to :5, whereas, with the "process of 'thetpresent invention values of .40 theoretical plates per foot of column length have been obtained in columns 1 /2 inches in diameter when freely :packed with .hollow ifilling'floo'dies made from woven :material.

Tests on distillation apparatus foperating "according to the process of the present invention have shown that with comparable vapour velocities, better efficiencies are obtained than with *distillation apparatus as hitherto "operated.

'Whenusinghollow fillingzbodies which'are freely packed, these 'eiliciencieszareaccompanied by unusually low liquid hold-up per theoreticalplate and-by very low pressure drop in the :column.

Figure 5 illustrates. .a distillation apparatus rsuitable for use :according to the process of "the as follows. ,zpacked lfor 536 :inches :of its .length with openended cylindrical Tfllling :bodi'es \inch by inch-made fromPhosphor bronzewiregauzehav- :ing wires per inch .the warp .and -in:.the weft.

6 present invention. 1a is .28. :column "freely :packed with hollow "filling ubodiesfmade bfi'om .woventmaterial, the column vbeing :connected 'to ,the .lboiler b. "Thor-reflux condenser 'clis :conne'cted to the column a by ili'mb :h. of 'a .Y piece :9 .while on 'the lirnb i of Y p'iece g .is a valve .dbynneans of i which samples 10f refiuxpliquor can be withdrawn through the limb f. v:l3etweenthe'boilerrbiand the .columnra .is anadjustable :orifice .e.

, Example 1 Y @App'aratus as hereinbeiore *described'wass-tested -A "5% inch :diameter zcolu'mn was The greatest dimension :of :such' a filling body :is along its diagonal and ;is about -;0."l-32 inch, giving, "withsthe l inch diameterz-column, a ratio :of column cross section to greatest aditmension of the filling bodies :of v5. 1, :i. we. not less *than 4:1. "The column was attached tto a 'bo'il'er :and both were :surrounded -:by :ia'ckets through which steam was passed, "whereby -isubstantially adiabatic conditions were maintained in the distillationvsystem.

A condenser was fittedto the top of the column. The liquidusedwasaibinary mixture of normal heptane withamethyl.cyclohexane. .After ,placing a :suitable quantity of :this liquid .in .the

boiler the packing was ;completely flooded with liquid gprior tot-testing by..heating the ,bo'ilertand partially closing :an adjustable orifice ii-11st bev.low the packing support, whereby ;-liquid soonadensed -in the column andifinoded :the packing. When flood-ing was complete the orifice was gradually opened to its fullest extent-and testing 'was commenced,.-the efliciency-of the column being determined .by ,the -.method .reierzredto by Lecky-w and Ewell in iIndustrial and v'lilngineering Chemistry Analytical Edition .1940, ..page

.544. .The results ;obtained are .shown .in Figlire-6.

The following .iurither examples illustrate the improvement obtained by operating-.accordingfto the :present invention, as applied .to distillation columns packed with various iillingb'odies, {the test liquid .used (in all .of the .examples being a mixture consistingapproximately .0: 20 parts by volume of n-heptane -311C11'805D31117S by volume of methyl cyclohexane. .II he vefliciency of .the

column being --investigated was .determined fiby -measuring -the refractive indicesof the .ltesti'liquid at-the commencement of the .testand o'fit'he reflux-liquidwhen the column was operatingunder steady conditions;at'-l00%.refluxmate, :i. e. without withdrawing-any substantial.quantitycotdistillate. By applying the readingsiorithere'fractive indices to the chart given by Lecky'and Ewell in Industrial and i- Engineering Chemistry Analytical Edition 12 .(1940) vat page 5117, the numberjdfftheoreticah plates in' the column under consideration iiwas determined. Injthe apparatus 'usediin the :following examples :the distillation column was fitted :it'o an "electrically "heated boiler andlprovided with. a reflux condenser at 'theitop. The column andboiler werefitte'dinto a "doublewalled (jacket to enable substantially adiabatic conditions to b'e :rnaintained' in the column and boiler.

7 Example 2 )A r distillation column, y-provided with :the slitscribed method A.

c'olumn allowed to return to'the' boiler. apparatus was kept'in operation until steady conditions were obtained when the efficiency of bronze wire gauzeihaving 60 meshes-to the. inch. Suificient test liquid-was placediin the. boiler and nary flooding. The number oftheoretical plates in the column was found to be equivalentito 3.9 theoretical-plates per foot. r

Using the "same apparatus, withthe column fitted at the bottom with an adjustable orifice, heating was applied to the boiler to give a distillation rate of1400 mls. per-hour and the adjustable orifice was partly closed so that the column became completely flooded with reflux liquid, as described under the hereinbefore de- Then, while maintaining the same rate of heating, the adjustable orifice was" gradually opened and th'eliquid in' the The the column was determined as above described. In 'thiscase', the number of theoretical plates in the column was equivalent to 10.7 theoretical plates per foot, i. e., an increaseof 6.8theoretical plates per foot. i I

.o Erampl e'tfff A distillation column 1 foot long by 1 inch ternaldiameter was fitted with packing as described in British patent specification No.

536,552 28 pairs of cones made from stainless steel wire gauze having 100 meshes to the inch being fitted into the column. Without making special provision to flood the column, heat was applied to the boiler to give a distillation rate of 500 mls. per'hour. The numberof theoretical "plates per foot was'found to be 2.5.

The apparatus was allowed to @5001 and drain,

" and was then restarted, but applying heat at such a rate that the column floodedwith liquid. The

supply of heat was then cut down to give a distillation rate of 500 mls. per hour, and when steady conditions were attained, it was found that ,the number of theoretical plates in the column was 6.2.]

After again allowing the column to cool and drain, the column was flooded bythe use of an adjustable orifice as described above (method A), the heat input being suflicient to give a distillation rate of 500 mls. er hour and when-steady conditions were attained the number of theoreticalplates per foot of column was found to be 7.5, an increase of 5.0 theoretical plates per foot as compared with operation with no preliminary flooding, and aninc'reas'e" of 1.3 theoretical plates per foot -when flooded by heating at a rate greater than th at required for the distillation process. W H F i Example-4 In thisexamplea column 9 mm. internal diameter and 45 cms. long was provided with a packing of the type described by Bower and to give a distillation rate of 150 mls. per hour.

hereinbefore described, using a, heat input sufficient to give a distillation rate. of mls.-per

hour. The quantity of liquid in the apparatus was such that when boiling, it completelyfilled the boiler and distillation--column. Then, without altering the heat'input, liquid was gradually removed from the boiler until about 100. mls. remained. When steady conditions -were--at tained, it was found that the number of theoretical plates in the column was equivalent to 11.6. per foot.

t Example 5 g r j The column used in this series of tests was 3 feet long and'had an internal diameter of '74; inch. It was packed with single turn helices made from wire 0.005 inches in diameten'the helices having a diameter of 1 s of-an inch.

Single turn helices of this type are' described by Fenske et al. in Industrial and Engineering Chemistry 26 (1934) at page 1169. Using a distillation rate of 750 mils. per hour and without any preliminary wetting the number of plates in the column was: equivalent to 10.0 plates per foot. When the packing was flooded by applying heatto the boiler at a rate greater than that which was used for the distillation the number of theoretical plates in the column was equivalent to 16.0 per foot, while when the packing; was flooded by the use of an adjustable orific'e asdescribed under method A hereinbefore given, the number of theoretical plates in the column was equivalent to 21.5 per foot.

'ExampZe 6-,

- A column 2 feet long and 1 inches indiameter was packed with fragments of expanded shale which passed through a inch mesh sieve but were retained on an /;'inch sieve. Using a distillation rate of 1400 mls. per hour and with no preliminary wetting of the packing the number of theoretical plates in the column" was equivalent to 2.4 plates per foot. When" the packing was flooded by applying heat to the'boiler at a rate greater than that which was used for the distillation, the number of theoretical plates in the column was equivalent to 5.4 plates per foot, while when the packing was flooded by the use of an adjustable orificeas described under method A hereinbefore given, the number of theoretical plates in the column was equivalent to 5.9 plates per foot. 1 In the appended claims the term gaseous is used to designate both substances which are gaseous under normal conditions of temperature and pressure and normally liquid substances in vapourized form. V

I claim: v 1. In a process forthe distillation of liquids in a distillation column fitted at the .top with a reflux condenser, at least part of the said distillation column being packed with substantially hollow filling bodies made from wire gauze, the apertures of the wire gauze being of such a size that they can be completely sealed by the liquid under the operating conditions, the ratio 1 of the smallest cross-sectional dimension of the packed portion of the column to the greatest dimension of the filling bodies at thatcross section being. at least 4 to l, the steps of passing the vapour of the liquid being treated from 'a boiler through a constriction into the distillation column, condensing the vapour in the said reflux condenser, returning the condensed liquid to the distillation column where it is prevented from returning to the boiler by the constriction, until the freely packed portion of the column is filled with liquid, adjusting the flow of condensed liquid returning to the column from the reflux condenser to an amount sufflcient to maintain the apertures of the filling bodies completely sealed, opening the constriction so that excess liquid returns to the boiler and maintaining the rate of flow of the vapour up the column sufliciently low not to break said sealing.

2. In a process for the distillation of liquids in a distillation column fitted at the top with a reflux condenser, at least part of the said distillation column being packed with filling bodies made from wire gauze, the apertures of the wire gauze being of such a size that they can be completely sealed-*by the liquid under the operating conditions, the steps of passing the vapour of the liquidbeing treated from a boiler through a constriction into the distillation column, condensing the vapour in the said reflux condenser, returning the condensed liquid to the distillation column where it is prevented from returning to the boiler by the constriction, until the packed portion of the column is filled with liquid, adjusting the flow of condensed liquid returning to the column from the reflux condenser to an amount sufficient to maintain the apertures of the filling bodies completely sealed, opening the constrictions so that excess liquid returns to the boiler, and maintaining the rate of flow of the vapour up the column sufficiently low not to break said sealing.

3. In a process for the distillation of liquids in a distillation column fitted at the top with a reflux condenser, at least part of the said distillation column being packed with forarninate material, the foramina of said material being of such a size that they can be completely sealed by the liquid under the operating conditions, the ratio of the smallest cross-sectional dimension of the packed portion of the column to the greatest dimension of the filling bodies at the cross section being at least 4 to 1, the steps of passing the vapor of the liquid being treated from a boiler through a constriction into the distillation column, condensing the vapor in the said reflux condenser, returning the condensed liquid to the distillation column where it is prevented from returning to the boiler by the constriction, until the freely packed portion of the column is filled with liquid, adjusting the flow of condensed liquid returning to the column from the reflux condenser to an amount suflicient to maintain the apertures of the filling bodies completely sealed, opening the constriction so that excess liquid returns to the boiler and maintaining the rate of flow of the Vapor up the column sufliciently low not to break said sealing.

i. In a process for the distillation of liquids in a distillation column fitted at the top with a reflux condenser, at least part of the said distillation column being packed with foramin-ate material, the foramina of said material being of such a size that they can be completely sealed by the liquid under the operating conditions, the steps of passing the vapor of the liquid being treated from a boiler through a constriction into the distillation column, condensing the vapor in the said reflux condenser, returning the condensed liquid to the distillation column where it is prevented from returning to the boiler by the constriction, until the packed portion of the column is filled with liquid, adjusting the flow of condensed liquid returning to the column from the reflux condenser toan amount sufficient to maintain the apertures of: the filling bodies completely sealed, opening the constrictions so that excess liquid returns to the boiler, and maintaining the rate of flow of the vapor up the column sufficiently low not to break said sealing.

5. In a process for the distillation of liquids in a distillation unit having a distillation column operated under reflux and having at least a part thereof packed with foraminate material possessing foramina of such size that they can be completely sealed by the distilled liquid under operating conditions tlje steps of flooding the column, deflooding the column and flowing vaporized liquid up the column, the maximum rate of said vapor flow at no time during the entire process being permitted to substantially exceed the rate employed in normal operation with the column in equilibrium, said flooding being accomplished by restricting the flow of reflux at a point below said packed section of said column while distilled vapors are allowed to pass up the column into the packed section from beneath said point and said deflooding being accomplished by discontinuing said restriction of the reflux flow after sufllcient liquid has accumulated in the packed section of the column to flood the same.

OLAF GEORGE DIXON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,208,573 Fenske July 23, 1940 2,317,101 Lecky Apr. 20, 1943 OTHER REFERENCES Publication, Industrial and Engineering Chemistry, vol. 15, pages 290 to 293, April 15, 194-3. 

1. IN A PROCESS FOR THE DISTILLATION OF LIQUIDS IN A DISTILLATION COLUMN FITTED AT THE TOP WITH A REFLUX CONDENSER, AT LEAST PART OF THE SAID DISTILLATION COLUMN BEING PACKED WITH SUBSTANTIALLY HOLLOW FILLING BODIES MADE FROM WIRE GAUZE, THE APERTURES OF THE WIRE GAUZE BEING OF SUCH A SIZE THAT THEY CAN BE COMPLETELY SEALED BY THE LIQUID UNDER THE OPERATING CONDITIONS, THE RATIO OF THE SMALLEST CROSS-SECTIONAL DIMENSION OF THE PACKED PORTION OF THE COLUMN TO THE GREATEST DIMENSION OF THE FILLING BODIES AT THE CROSS SECTION BEING AT LEAST 4 TO 1, THE STEPS OF PASSING THE VAPOUR OF THE LIQUID BEING TREATED FROM A BOILER THROUGH A CONSTRUCTION INTO THE DISTILLATION COLUMN, CONDENSING THE VAPOUR IN THE SAID REFLUX CONDENSER, RETURNING THE CONDENSED LIQUID TO THE DISTILLATION COLUMN WHERE IT IS PREVENTED FROM RETURNING TO THE BOILER BY THE CONSTRUCTION, UNTIL THE FREELY PACKED PORTION OF THE COLUMN IS FILLED WITH LIQUID, ADJUSTING THE FLOW OF CONDENSED LIQUID RETURNING TO THE COLUMN FROM THE REFLUX CONDENSER TO AN AMOUNT SUFFICIENT TO MAINTAIN THE APERTURES OF THE FILLING BODIES COMPLETELY SEALED, OPENING THE CONSTRUCTION SO THAT EXCESS LIQUID RETURNS TO THE BOILER AND MAINTAINING THE RATE OF FLOW OF THE VAPOUR UP THE COLUMN SUFFICIENTLY LOW NOT TO BREAK SAID SEALING. 